Method of remanufacturing spent catalyst for heavy oil desulfurization

The present application claims priority to Korean Patent Application No. 10-2023-0048228, filed on Apr. 12, 2023, the entire contents of which is incorporated herein for all purposes by this reference.

The present disclosure relates to a method of remanufacturing a spent catalyst for heavy oil desulfurization. More particularly, the present disclosure relates to a method of remanufacturing a spent catalyst for heavy oil desulfurization, in which the spent catalyst that is to be discarded or buried due to reduced catalytic activity is used as a substitute for a fresh catalyst through a series of processes for reuse.

A catalyst for heavy oil desulfurization, used in a hydrodesulfurization process of heavy oil or residual oil, is used to reduce viscosity and improve combustibility and reactivity in a fluid catalytic cracking process by removing impurities, such as sulfur and heavy metals (mostly vanadium) contained in the heavy oil.

Petroleum, currently the largest energy source for humankind, is refined through various processes for use. Although demand for light oil is increasing, crude oil itself tends to become heavier. Accordingly, not only Korea but also developed countries have made a great deal of investment in advanced refining facilities, referred to as secondary oil fields in Korea. However, new investment is currently depressed because the crude oil refining industry is shrinking due to eco-friendly and decarbonization trends. Nevertheless, the reality is that upgrading facilities are essential to reduce dependence on high-quality crude oil and ensure profitability with low-quality crude oil.

As the running time of the desulfurization process elapses under conditions of high temperatures and high pressures, sulfur and heavy metals, such as vanadium, contained in the heavy oil and coke components generated during the process are gradually deposited on the catalyst. Due to the deposition, the entrance of the catalyst micropores impregnated with active ingredients is completely blocked. Accordingly, the heavy oil and the active ingredients are blocked from being in contact with each other, leading to a point where the reaction can no longer occur. As a result, the catalyst reaches the end of its life. In addition, the replacement cycle is considerably short, approximately less than one year.

The spent catalyst that has reached the end of its life as a catalyst is crushed to collect only valuable metals, or buried when being economically infeasible. This may cause a problem of contaminating groundwater or the like as designated waste due to the elution of heavy metals contained in the spent catalyst. Therefore, it is urgent to propose a method for reusing the spent catalyst for the heavy oil desulfurization process.

Hence, various regeneration methods of spent catalysts for heavy oil desulfurization have been proposed. For example, in International Patent Publication No. WO1999/061557, proposed is a regeneration method of a spent catalyst through processes of washing the catalyst with a solvent and then removing carbonized material by performing heat treatment at a temperature in a range of 200° C. to 800° C. In addition, disclosed is a method of performing a desulfurization process by allowing heavy oil to pass through a reactor filled with regenerated the catalysts through the regeneration method.

However, such heat treatment removes only the deposited carbonized material and sulfur components through oxidation, so the deposited vanadium components are not removed and keep blocking the entrance of catalyst the micropores. Accordingly, the desulfurization performance may be temporarily restored. Still, there is a problem in that the desulfurization performance is unlikely to be continuously maintained for a long time corresponding to the original life of a fresh catalyst.

Hence, in Korean Patent No. 10-1434437, proposed is a method of regenerating a spent catalyst by washing the spent catalyst with a solvent, performing heat treatment at a temperature in a range of 400° C. to 550° C. to remove sulfur and carbonized material, and then removing vanadium using a solvent.

The catalyst regenerated through such a regeneration method has the advantage that the deposited vanadium component is completely leached and removed. However, a significant amount of active ingredients, molybdenum and nickel, are also lost at the same time. As a result, a sufficient level of catalytic activity as a catalyst fails to be exhibited. In addition, since the catalyst is regenerated in a solution or slurry phase, separate processes of leaching, washing, and drying are necessary, and thus the costs increase. As a result, there is a limitation in that economic feasibility fails to be practically ensured by catalyst regeneration.

The present disclosure has been made to solve the above problems, and the main objective of the present disclosure is to provide a method of remanufacturing a spent catalyst for heavy oil desulfurization. The regeneration method not only can minimize the loss of catalytically active ingredients without involving leaching, washing, and drying processes but also can economically manufacture a catalyst having desulfurization performance and specific surface area that are equivalent to those of a fresh catalyst.

In order to accomplish the above objective, an embodiment of the present disclosure provides a method of remanufacturing a spent catalyst for heavy oil desulfurization. The remanufacturing method includes: (a) performing heat treatment on a spent catalyst for heavy oil desulfurization, (b) performing dry mixing by adding a spinel-structured metal oxide represented by Formula 1, a solid polycarboxylic acid, and a catalytically active material precursor to the spent catalyst obtained through the heat treatment, and (c) performing calcination of the resulting mixture obtained by the dry mixing.XAlO  [Formula 1]

In Formula 1, X is Ni, Cu, or Zn.

In a preferred embodiment of the present disclosure, in the (a) performing, the heat treatment may be performed at a temperature in a range of 250° C. to 350° C.

In a preferred embodiment of the present disclosure, in the (b) performing, the spinel-structured metal oxide represented by Formula 1 and/or the solid polycarboxylic acid may be added to perform a first dry mixing, and then the catalytically active material precursor may be added to perform a second dry mixing.

In a preferred embodiment of the present disclosure, in the (b) performing, 0.1 to 5 parts by weight of the spinel-structured metal oxide represented by Formula 1, 0.5 to 15 parts by weight of the solid polycarboxylic acid, and 0.5 to 15 parts by weight of the catalytically active material precursor may be added, with respect to 100 parts by weight of the spent catalyst obtained through the heat treatment.

In a preferred embodiment of the present disclosure, in the (b) performing, the dry mixing may be performed by mechanical mixing.

In a preferred embodiment of the present disclosure, the mechanical mixing may be performed by milling at a rotation speed in a range of 100 rpm to 300 rpm in an inert atmosphere.

In a preferred embodiment of the present disclosure, the solid polycarboxylic acid may be at least one selected from the group consisting of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, terephthalic acid, isophthalic acid, homophthalic acid, and phenyl glutaric acid.

In a preferred embodiment of the present disclosure, the catalytically active material precursor may include at least one selected from the group consisting of: at least one metal selected from the group consisting of molybdenum, tungsten, cobalt, and nickel; oxides of the at least one metal selected from the group; and mixtures of both.

In a preferred embodiment of the present disclosure, in the (c) performing, the calcination may be performed at a temperature in a range of 450° C. to 600° C.

In a preferred embodiment of the present disclosure, a regenerated catalyst remanufactured thereby may have a desulfurization performance of 97% or higher with respect to that of a fresh catalyst.

In a preferred embodiment of the present disclosure, a regenerated catalyst remanufactured thereby may have a specific surface area of 97% or higher with respect to that of a fresh catalyst.

According to the present disclosure, when performing mechanical dry mixing by adding a spinel-structured metal oxide, a polycarboxylic acid, and a catalytically active material to a spent catalyst for heavy oil desulfurization obtained through heat treatment performed at low temperatures, the loss of catalytically active ingredients can be minimized, without involving leaching, washing, and drying processes. In addition, a specific surface area can be maintained at a level equivalent to that of a fresh catalyst, so a catalytic activity equivalent to that of the fresh catalyst can be obtained in a hydrotreating process of heavy oil or residue oil, especially in a desulfurization process. Furthermore, the remanufactured catalyst of the present disclosure can exhibit a better catalytic activity than catalysts regenerated through existing regeneration processes and thus can be perfectly usable as an alternative catalyst for the fresh catalyst.

Advantages and features of the present disclosure, and methods for achieving them will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments set forth below and will be implemented in many different forms. The following embodiments are provided only to completely disclose the disclosure and inform those skilled in the art of the scope of the present disclosure. In addition, the present disclosure is defined only by the scope of the appended claims.

The term “heavy oil” or “residual oil” mentioned herein regarding petroleum products refers to oil including distillation residues, such as atmospheric residual oil, vacuum residual oil, and the like, but does not include oil composed only of split oil, such as kerosene, diesel oil, vacuum gas oil, and the like.

As the terms regarding a catalyst, “fresh catalyst”, “spent catalyst”, and “regenerated catalyst” are used herein, and the definitions thereof are as follows.

First, the term “fresh catalyst” mentioned herein means a catalyst manufactured for use in a desulfurization process of heavy oil or residual oil. The fresh catalyst includes catalysts that have never been used in the desulfurization process as well as catalysts that were once used for the desulfurization process but stopped for use in a short time due to equipment problems and used again as they were. In other words, the fresh catalyst includes catalysts that still have a sufficient hydrotreating activity considered from the outset, even when being temporarily used or without involving a specific activation process.

The term “spent catalyst” mentioned herein means a catalyst that has been used in the desulfurization process of heavy oil or residual oil, and is no longer capable of obtaining sufficient desulfurization activity.

The term “regenerated catalyst” mentioned herein means an activated catalyst obtained by removing impurities from the spent catalyst according to the remanufacturing process of the present disclosure.

The spent catalyst, the fresh catalyst, and the regenerated catalyst mentioned herein are supported catalysts having a form in which catalytically active materials and a carrier supporting the same are contained.

The catalytically active materials, which are components substantially exhibiting catalytic activity, may include a transition metal. For example, the catalytically active materials may include at least one selected from the group consisting of: at least one metal selected from the group consisting of molybdenum, tungsten, cobalt, and nickel; oxides of the at least one metal selected from the group; and mixtures of both.

On the other hand, the carrier, used for supporting the catalytically active materials, functions to support and disperse the catalyst to increase the surface areas thereof, stabilize the catalyst, and reduce the cost of the catalyst. The carrier itself has no activity but affects the catalytic activity due to the functions described above. In addition, even with the same composition, there may be a significant difference in catalytic activity depending on the amounts of supported active ingredients. Therefore, the selection of the carrier also needs to be taken into account.

In the present disclosure, any material capable of being applied to a carrier of the catalyst for a desulfurization process may be used as the carrier. For example, at least one selected from the group consisting of activated carbon, zeolite, AlO, SiO, and ZrOis available. Specifically, AlOmay be used.

The amounts of the catalytically active materials being lost may be minimized after the completion of the remanufacturing process. As a result, the regenerated catalyst, according to the present disclosure, may have a specific surface area that is restored to a level equivalent to that of the fresh catalyst and exhibit desulfurization performance so as to be practically applied to the desulfurization process. Such effects are to be achieved by the remanufacturing method described below.

In the present disclosure, provided is a method of remanufacturing a spent catalyst for heavy oil desulfurization, which includes: (a) performing heat treatment on a spent catalyst for heavy oil desulfurization, (b) performing dry mixing by adding a spinel-structured metal oxide represented by Formula 1, a solid polycarboxylic acid, and a catalytically active material precursor to the spent catalyst obtained through the heat treatment, and (c) performing calcination of the resulting mixture obtained by the dry mixing.XAlO  [Formula 1]

In Formula 1, X may be Ni, Cu, or Zn.

In the method of remanufacturing the spent catalyst for heavy oil desulfurization according to the present disclosure, heat treatment is first performed on a spent catalyst for heavy oil desulfurization [(a)].

In an existing process of regenerating a spent catalyst for heavy oil desulfurization, the heat treatment is performed at a high temperature of 400° C. or higher to remove carbon and sulfur deposited on the spent catalyst, and then heavy metals, such as vanadium, are removed. In such a process, high-temperature heat treatment is first performed when the deposition amount of vanadium is large, so the vanadium component acts as an oxidation catalyst. In other words, sulfur dioxide generated during the oxidation of metal present in the form of a sulfur compound is oxidized, thereby facilitating sulfur trioxide to be produced. In addition, Al(SO)is formed by the reaction between AlO, serving as a carrier, and sulfuric acid generated by the reaction between sulfur trioxide and moisture, so the mechanical strength of the catalyst is likely to be deteriorated. In addition, reaction heat generated by the exothermic reaction fails to be released to the outside of the catalyst micropores and thus is trapped inside the micropores. Accordingly, a rapid local temperature rise makes temperature control difficult. Furthermore, there may be problems in that active ingredients, molybdenum and nickel, aggregate to each other, thereby reducing the specific surface area, and the loss of active sites deteriorates the desulfurization performance.

Hence, in the present disclosure, carbon and sulfur deposited in the spent catalyst may be removed by low-temperature heat treatment to avoid problems caused when performing heat treatment at high temperatures in a state where the deposition amount of vanadium is large.

The low-temperature heat treatment may be performed at a temperature in a range of 250° C. to 350° C., preferably in the range of 280° C. to 320° C., for 2 hours to 5 hours, and more preferably in the range of 290° C. to 310° C. for 2 hours to 4 hours. When the temperature and time of the heat treatment fall within the above numerical ranges, the carbon and sulfur deposited in the spent catalyst, used for preventing condensation of the active ingredients and exhibiting a catalytic activity equivalent to that of the fresh catalyst, may be removed.

On the other hand, removing heavy oil or residual oil remained in the spent catalyst using a solvent may be further performed before performing the low-temperature heat treatment described above. The solvent used for the removing is not particularly limited in the present disclosure, and any solvent capable of easily dissolving a known petroleum product may be used. For example, the solvent may be at least one selected from the group consisting of: aliphatic hydrocarbons, such as pentane, hexane, heptane, and isooctane; alicyclic hydrocarbons, such as cyclohexane; aromatic hydrocarbons, such as benzene, toluene, xylene, and styrene; naphtha; kerosene; and a mixed solvent thereof. Preferably, kerosene or heptane corresponding to an aliphatic hydrocarbon that is not highly volatile and is inexpensive may be used.

The removing of the heavy oil or residual oil is not particularly limited in temperature and may be performed one or more times under conditions of room temperature and normal pressure. Preferably, the removing may be performed three or more times with temperature application to sufficiently remove the heavy oil or residual oil. Depending on the devices, methods such as immersion and spraying may be used, and a batch or continuous process may be performed.

Drying for removing the residual solvent may be performed after removing the heavy oil or residual oil. Then, the dried spent catalyst may be subjected to the low-temperature heat treatment. In this case, the temperature and time of the drying are not particularly limited and may vary depending on the types of solvent. For example, the drying may be performed at a temperature in a range of 60° C. to 180° C. for 1 hour to 24 hours.

Next, dry mixing is performed by adding a spinel-structured metal oxide, a solid polycarboxylic acid, and a catalytically active material precursor to the spent catalyst for heavy oil desulfurization obtained through the heat treatment [(b)].

The term “spinel structure” used herein typically means a structure having a form in which metals, X and Y, are present in a cubic crystal form of XYO, oxygen anions are arranged in a cubic close-packed lattice, and the cation metals, X and Y, occupy some or all of the octahedral and tetrahedral sites in the lattice.

In the present disclosure, the spinel-structured metal oxide, especially applicable to the remanufacturing of the spent catalyst for heavy oil desulfurization, may be at least one of NiAlO, ZnAlO, and CuAlOthat satisfy Formula 1, which is an aluminum-based spinel structure having a large surface area as well as excellent mechanical strength, acid resistance, and heat resistance. Preferably, the metal oxide is NiAlO.

A currently available product or a product obtained by manufacturing the same may be used as the spinel-structured metal oxide. In this case, any manufacturing method known in the art may be used without limitation.

The spinel-structured metal oxide may have an average particle size in a range of 100 nm to 1,000 nm, preferably in the range of 500 nm to 1,000 nm. When the average particle size of the spinel-structured metal falls within the above numerical range, the surface area may be large enough to control heat generation easily during the reaction.